Many government, industrial, and commercial entities have a need to protect various aspects of their endeavors from hostile physical intrusion. Such intrusions may range from terrorist attacks to burglary attempts to mischievous mayhem to industrial or military espionage. To prevent such actions it is often desirable to secure the property boundaries at sensitive sites such as nuclear and chemical facilities, military bases, and other sensitive installations. Sometimes such protection focuses on a boundary of a particular facility such as a warehouse, a vault, a storage crib, or a similar protected zone. In some instances a security system may be employed to monitor a physical boundary associated with such a system. For example, a fence around a protected property may include an electronic continuity circuit that is designed to detect a break in the fence that could indicate an intrusion into the property. In some instances a security system may be employed to monitor the physical integrity of a secured space. Examples of such security systems are window and door alarms, motion detectors, and optical beam interruption detectors. Also, distribution systems such as gas and oil pipelines, electrical distribution systems, and voice and data communication lines often warrant special security measures. In the case of pipelines, fluid pressure monitors may be used to detection intrusion of the boundary (i.e., the path) of a pipeline. In the case of electrical power distribution systems and communication systems, the detection of service interruption may be used to detect tampering with the “boundary” (i.e., the distribution/communication lines) associated with such systems. However in the case of communication lines it is often necessary to also protect against eavesdropping, and various detection systems have been developed for that purpose. However adversary nations, terrorists, rogue organizations, and thieves are becoming increasingly technically sophisticated in their abilities to attack and thwart such security measures. What are needed therefore are improved security systems for protecting various boundaries and communication lines from compromise by such attacks.